Profile corrector



April 15, 1958 c. s. HARRIS PROFILE CORRECTOR Filed April 22. 1954 INVENTOR f/are S. Harr/s ATTORNEYS.

PROFILE CORRECTOR Clare S. Harris, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application April 22, 1954, Serial No. 424,899

4 Claims. (Cl. 153-32) This invention relates to the extrusion of light metals and alloys, and particularly to profile correctors for use in association with'extrusion dies.

Extrusions of light metals, such as aluminum, magnesium, and their alloys, particularly those of unsymmetrical shape or non-uniform wall thickness, often do not have the correct profile as they leave the extrusion die.

. The thickness of the various sections may be within tolerance limits, but their angularity or alignment may be incorrect, e. g, flanges might be curved or bent out of angularity. Likewise, the sections may be warped longitudinally instead of being straight.

Such imperfections in profile and straightness are due to stresses on or within the metal as it emerges from the die. Temperature stresses are particularly detrimental. Other irregular stresses result from uneven rates of flow of metal in different parts of the die or from pulling, twisting, or sagging of the shape immediately after it leaves the die.

While some causes of incorrect profile in extrusions have been mentioned above, the basic causes of warping of the extrusion may be hard to determine during production operations. For example, uneven rates of flow of the metal in different parts of the die may result from improper heating of the billet being extruded, or poor die design in which the friction is greater in one part of the die than in another. The shape of the extrusion itself may be such that unequal rates of flow of metal through the die causes the extrusion to be warped.

Heretofore such imperfections in the profile of extruded materials have been minimized by careful handling and adjustment of extrusion conditions and die design, or by corrective measures such as stretching to correct longitudinal curvature, either as the extrusion leaves the die or after the extrusion is cold. These methods are troublesome, time consuming, and often unsatisfactory even though careful control of all aspects of the extrusion process is maintained. In some cases it has been impossible to extnlde complex shapes suitable for commercial orders, solely because of improper profile.

In some cases drawing dies made of tool steel have been used to correct shapes or profiles of extrusions of light metals. The imperfect extrusion is drawn through such dies to improve alignment of flanges and other profile defects either with or without a small amount of thickness correction or sizing. This practice has notproven entirely satisfactory because the dies are not adjustable and because the hard die metal scufis and scratches the extrusion. Furthermore, since the operation is usually done when the extruded section is cold, there i a certain amount of springback which cannot be accurately anticipated by the design of the draw die.

The cold drawing of extrusions to correct their profile is also subject to the objection that profile correction is a separate operation from the extrusion operation. This makes the finished product more costly, and sometimes makes profile correction by cold drawing commercially the unprofitable even though scufling and scratching of the extrusion couldbe tolerated.

As a substitute, drawing of the extrusion through separate dies just after it leaves the extrusion press has been attempted in the past. However, in addition to the scufiing and scratching of the extrusion which was present in cold drawing, other difiicultie have arisen. Considerable force is required to draw the extrusion through the die, and close coordination between the rate of extrusion from the press and the rate of drawing the extrusion through the die has even further complicated an already complicated process. Thus, it has appeared that if drawing of an extrusion through a die to correct the profile of the extrusion is to be used, it can best be done as an operation which is entirely separate from the extrusion and runout process.

In both hot and cold drawing, the drawing dies are lubricated, and removal of the lubricant from the extrusion constitutes a further operation.

Finally, because of the large variety of sections which may be extruded, the stock of profile-correcting metal draw dies necessary to the production of so many different sections would represent a considerable investment.

Another attempt at correcting the profile of extrusions has been to place rollers against those sections of the extrusion which were improperly aligned. The rollers apply pressure which tends to force the warped or misshapened section back into its proper position. This method, up to the present time, at least, has met with but slight commercial success because expensive and complicated mounting is required to adapt such rollers quickly to a wide variety of extrusions. Furthermore, it is very difficult, if not impossible, to use rollers to correct the profile of small sections having re-entrant angles. Also, some light metal alloys, particularly some of the alloys of magnesium, are not well adapted, due to their hexagonal crystal structure, to cold working either by die rawing or by cold rolling processes.

Accordingly, a principal object of this invention is to provide an improved means for and method of correcting the profile of extrusions of light metal alloys.

Another object of this invention is to provide an improved, readily adjustable means for correcting the profile of extrusions of light metal alloys.

A further object of this invention is to provide an improved, self lubricating means for correcting the profile of sections of light metal alloys which does not scuff, scratch or mar the surface thereof.

Yet another object of this invention is to provide improved profile correcting means for sections of light metal alloys which is adapted for use in conjunction with the die means for forming the section whereby the section is formed and its profile corrected in a single continuous operation.

An ancillary object of this invention is to provide an improved profiling device in which the part thereof which bears against the extrusion may be easily and economically replaced in event of breakage.

The above and related objects are achieved in accordan opening which closely approximates the shape of the extrusion die opening. Each of the graphite fingers or elements is adjustahly mounted on a hacker plate, in order to permit adjustment in the amount of correction in a particular portion of the section. The extrusion is drawn through the profiler with a moderate force which tends to remove longitudinal curvature of the extruded section and to correct any transverse warping.

The invention, as well as additional objects and advantages thereof will best be understood when the following detailed description is read in connection with the accompanying drawing, in which:

Fig. '1 is a diagrammaticand side elevational sectional view of extrusion and profile correcting apparatus in accordance with the present invention;

Fig. 2 is an exploded isometric view of profile correcting apparatus in accordance with this invention;

Fig. 3 is an isometric view of one of the graphite fingers or elements of the profile corrector shown in Fig. 2, and

Fig. 4 is a simplified, fragmentary side elevational view, in section, of an extrusion press having a profiler mounted on a runout frame in accordance with. the present invention.

Referring to Fig. 1, there is shown an extrusion press having a working cylinder 12, a die 14, a ram 16, and a bolster 18 holding the die against the force of the extrusion process.

Adjoining the extrusion press 10 is a profile corrector 20 through which the extrusion 22 passes, the end 24 of the extrusion being clamped to a cable 26 and winch 28 or other means for maintaining the extrusion 22 under tension as it leaves the die 14 and passes through the profile corrector or profiler 20.

The press 10, profile corrector 20 and Winch or draw works 28 are each secured to a foundation, which for the sake of simplicity is not shown.

The profile corrector 20 is secured to a mounting member or frame 30 and so positioned that the portion 32 of the profiler 20 through which the extrusion 22 passes is substantially in axial alignment with the die 14.

Referring more particularly to Figures 2 and 3, the profiler 20 includes a metallic backer plate 34 of sufficient thickness to be rigid when under tensions of the magnitude to which it will be subjected. A typical backer plate will be made of metal plate which is A" or 'Zs in thickness. Thicker backer plates may sometimes be called for in the case of a wide extruded section.

The backer plate 34 is bolted or otherwise secured to the mounting member 30, the bolts passing through the apertures 36 which are located near the periphery of the backer plate. A cut out portion 3%, which usually approximates thecontour of the extrusion die but is somewhat larger in area so that the extrusion will pass freely through the opening, is disposed in the central portion of the backer plate. Mounted on the plate are segments or fingers 40 each of which contains at least one slot 42 through which it is bolted to the hacker plate 34 through a suitably located bolt hole 44- therein. The slot 42, which extends lengthwise of the segment, permits spatial adjustment of the segment. The segments. 40, when assembled together and mounted on the backer plate 34, define an opening 32 which closely corresponds to the opening of the extrusion die 14. That is, each of the segment ends which bear against the extrusion are shaped to fit the contour of a portion of the extruded section. The segments 40 are often slightly beveled as well as shaped to fit the contour of the section as mentioned above, so that the opening 3-2 is larger on the face of the graphite blocks or segments facing the press although the cross sectional configuration of the opening 32 is approximately the same on either face of the segments or fingers 4E The thickness of all segments in a profiler is normally the same, but the segment thickness may vary between 1 and 12 inches, for example. Usually, however, adequate correction of profile may be obtained with segment thicknesses of 3 inches or less. It will be appreciated that the thickness dimension depends on the stress on the segment and also upon the rate of change of profile which is intended as .the extrusion 22 passes through.

It should also be noted that although the segments 4% are illustrated as being bolted to the backer plate 34, they could likewise be clamped into position. i

The extrusion press 10 and profile corrector or profiler 20 function as follows. An extruded section 22 is formed as the ram 16 forces metal from the billet 44 through the die 14. As mentioned previously, due to one or more of a variety of causes, some of which may be beyond the control of the press operator, the extrusion may tend to warp and distort the profile of the section. The extrusion 22 is fed through the profiler 20 and the individual segments 40 thereof, which were previously contoured similarly to the extrusion die opening, are adjusted to overcome the warpage of the extrusion and provide the extrusion with the correct profile when it cools.

The extrusion is drawn. by the cable 26 and winch or draw works 28, under tension of the order of magnitude required to correct longitudinal warpage, through the profiler to overcome the frictional resistance thereof and to correct longitudinal curvature of the extrusion 22.

It should be realized that the opening 32, defined by the space between the rows of segments 40, is not necessarily symmetricalwith the opening of the extrusion die 14. On the contrary, a severe distortion of the extruded section may dictate what might be called an apparent over correction of the warpage in order that when the extruded section is cooled it will have the proper contour.

In some applications, it is desirable that the profile corrector 20 be located quite close to the die 14. This is especially true when extrusions of thin cross sectional thickness are made, since such sections tend to cool quickly. It is impractical at times, however, to mount the profile corrector 29 as close to the die 14 as desired, since any saw used in cutting off the extrusion is normally mounted close to the die.

As shown in Fig. 4, the profile corrector 20 is mounted adjacent to an end 48 of a runout frame 50, which is mounted on rollers 52 so that as the metal is being extruded the profile corrector 20 is positioned close to the die 14. The profile corrector may be withdrawn, as the runout frame is withdrawn, however, to allow the extrusion cutting saw to swing into operating position and to permit other adjustments of the press. In any event, it is desirable that some articulation be provided in mounting the profiler 20 so that it may adjust itself to the general shaping and angularity of the extruded work piece without bending or kinking it.

Graphite segments provide sufiicient strength to withstand the pressure required for hot working of the extrusion, are self lubricating and do not mar the extrusion, are easy to machine to the desired shape, and are economical and easily available.

Further, graphite profile segments have a long useful life, as they wear very slowly. Because the extrusion is still hot and soft as it passes between the segments 49, it is easily deformed without great pressure and with no problems due to spring back. Graphite, as mentioned herein, is intended to include mixtures or alloys which are predominantly composed of graphite.

Likewise, if needed, the graphite segments could be water cooled, by providing water grooves in the graphite surfaces adjacent to the extrusion, in order to cool the die and quench the extrusion.

Thus, the present invention provides a flexible, economical, and convenient means for correcting or altering the profile of extruded sections of light metals, particularly alloys of magnesium and aluminum.

I claim:

1. Apparatus for correctingthe profile of, an extruded section of a light metal, said apparatus comprising a metal backing plate having an aperture extending through the thickness dimension thereof, saidaperture being of sufiicient size to permit the freepassage therethrough of an extruded section, a plurality of graphite segments disposed generally around theopening and having surfaces adapted-to bearagainst saidsection and defining the general profile desired of the extruded section, said segments being secured to said backing plate.

2. Apparatus for correcting the profile of an extruded section of a light metal, said apparatus comprising a metal backing member having an aperture extending through the thickness dimension thereof, said aperture being of sufiicient size to permit the free passage therethrough of an extruded section, two rows of graphite segments, the space between the two rows of segments defining the general profile desired of the extruded section, sm'd rows of segments being secured to said backing plate, said backing plate being so disposed with respect to the extruded section that said section is aligned with the space between said rows of segments.

3. Apparatus for correcting the profile of an extruded section of light metal, said apparatus comprising a plurality of graphite segments having surfaces adapted to bear against surfaces of said section and defining the general profile desired of said section, and mounting means to which said segments are secured.

4. Apparatus in accordance with claim 3, wherein the spatial position of said segments may be individually adjusted.

References Cited in the file of this patent UNITED STATES PATENTS 

1. APPARATUS FOR CORRECTING THE PROFILE OF AN EXTRUDED SECTION OF A LIGHT METAL, SAID APPARATUS COMPRISING A METAL BACKING PLATE HAVING AN APERTURE BEING OF THE THICKNESS DIMENSION THEREOF, SAID APERTURE BEING OF SUFFICIENT SIZE TO PERMIT THE FREE PASSAGE THERETHROUGH OF AN EXTRUDED SECTION, A PLURALITY OF GRAPHITE SEGMENTS 